c# I have CheckBoxes and when i run and click them they don't appear with a check mark, even though if they are enabled

Basically I made a simple schedule for grade 7 so I be sure that I completed every task so I made checkboxes, and then I ran it and the checkboxes where not getting checked, and yes, they where enabled

private void CheckBox16_CheckedChanged(object sender, EventArgs e) {

            button1.Enabled = true;

    }